There are four stages of syphilis: the primary, secondary, latent, and tertiary stages. In each stage, the signs and symptoms of syphilis are different.

In the primary stage, a person usually just has a wound on their skin, called a "chancre." In the secondary stage, a person usually gets a rash. In the "latent" stage, syphilis has few or no symptoms. If syphilis reaches the tertiary stage, which is the most severe, it causes many serious symptoms. These can include problems with the nervous system (the brain and nerves) and problems with the heart. Eventually, many people with tertiary syphilis will die if they do not get medical treatment.

Syphilis is usually diagnosed with blood tests. The bacteria that causes syphilis can also be seen under a microscope. Most people who have syphilis can be treated and cured with antibiotics.

By 1999, more than 12 million people around the world had gotten syphilis. More than 90% of these people (10.8 million) lived in the developing world.[1] Syphilis got much less common after penicillin became available in the 1940s. At that time, penicillin was used as a treatment for syphilis, and often cured the disease. However, since 2000, syphilis is becoming more common again.[1]

Syphilis can be a very dangerous disease if it is not treated. Without treatment, 8% to 58% of people with syphilis die from the disease. Syphilis also makes a person two to five times more likely to get Human Immunodeficiency Virus (HIV).[1][2]

After a person gets syphilis, the disease begins in the primary stage. A person gets syphilis by having sex with a person who has syphilis. Usually, the person who has syphilis has wounds on their genitals caused by syphilis. Touching these wounds during sex (including oral sex or anal sex) can give a person syphilis.[3]

Later, a chancre (skin sore) usually appears at the place on the body that touched the infected wounds.[2] The chancre can be painful. The most common type of chancre gets bigger and bigger until it becomes an ulcer.[4]

Chancres can appear in places other than the genitals. In women, chancres most often appear on the cervix - the bottom of the uterus. Some people get no chancres at all. Many people who have secondary syphilis (40–85% of women and 20–65% of men) say they never had a chancre during the primary stage.[5]

Around the place where syphilis entered the body, the lymph nodes usually get bigger[2] about 7 to 10 days after the chancre forms.[4] If the person does not get treatment, their wound(s) can last for three to six weeks.[2]

Secondary syphilis can cause rash-like sores on the palms of the hands.

Reddish papules and nodules over much of the body due to secondary syphilis

If a person does not get treatment, syphilis will get worse. The secondary stage of syphilis will start about four to ten weeks after the person first got infected.[2] Secondary syphilis can cause many different symptoms. However, the most common three symptoms are:[5]

In the latent stage of syphilis, a person has no symptoms, but blood tests show that he has syphilis.[3] Latent syphilis is described as either early or late.

The early latent stage: In the United States, latent syphilis is called "early" if it has been less than one year since the person had secondary syphilis.[7] In the United Kingdom, latent syphilis is called "early" if it has been less than two years.[4]

In this stage, the symptoms of secondary syphilis can still come back.

The late latent stage: People enter this stage when it has been more than one year (in the U.S.) or more than two years (in the U.K.) since they had secondary syphilis.

People in this stage have no symptoms, and do not spread syphilis as easily as people in the early latent stage.[7]

If a person with syphilis does not get treatment, the disease can reach the worst stage - tertiary syphilis. Usually this happens about three to 15 years after the person first got infected. Without treatment, one-third of people with syphilis get tertiary disease.[7] People with tertiary syphilis cannot infect other people with syphilis.[2]

Gummatous syphilis can happen anywhere from one to 46 years after the person first got syphilis. On average, it happens after 15 years. It causes soft, tumor-like balls of inflammation (swelling), of many different sizes. Usually they appear on the skin, bone, and liver, but they can happen anywhere.

About 15% of people who do not get treated for syphilis get gummatous syphilis.

In neurosyphilis, the syphilis infects the central nervous system (the brain and spinal cord). In some people, neurosyphilis happens soon after they get syphilis. (This is called early neurosyphilis.) Some of these people have no symptoms of neurosyphilis. Others get syphilitic meningitis, a dangerous infection of the meninges (the protective layers which line the brain and spinal cord).

Neurosyphilis can also appear later, usually four to 25 years after a person first got syphilis. (This is called late neurosyphilis.) Late neurosyphilis can cause many serious problems. For example:

The most common problem it causes is syphilitic aortitis, which affects the aorta. The aorta is the most important artery in the heart; it helps carry blood to the entire body. Syphilitic aortitis can make the aorta become too big.[2] If the aorta is too big, it cannot work correctly.

About 10% of people who do not get treated for syphilis get cardiovascular syphilis.

If babies with syphilis do not get treated, they can get late congenital syphilis, which has much more serious symptoms. For example, the child can have seizures, and their body and brain may not grow normally.[8]

Syphilis is caused by the Treponema pallidum bacterium. Treponema pallidum is a species of bacterium which is shaped like a spiral: a spirochaete.[9] There are different types of Treponema pallidum bacteria, which are called subspecies.[8]

Scientists think that Treponema pallidum can only live inside humans.[1] The bacterium cannot survive outside a human for more than a few days.

Syphilis is spread mostly by sexual contact or during pregnancy from a mother to her fetus. Syphilis can pass through undamaged mucous membranes, or through damaged skin.[1][2] Because of this, syphilis can be spread through oral sex, vaginal sex, and anal sex.[2] It can also be spread by kissing, if the person with syphilis has a sore in their mouth.[2]

Only a very small amount of the Treponema pallidum bacterium needs to get into a person's body to cause syphilis. However, not everybody who is exposed to primary or secondary syphilis will get the disease.[7]

A person can get syphilis if they get a blood transfusion from someone with the disease. However, many countries test blood donations for syphilis. In countries that do not do this, getting syphilis from a blood transfusion is much more likely.

It is hard for doctors to diagnose syphilis just from the signs and symptoms that happen early on, because many diseases can cause skin sores and rashes.[4] Instead, they can diagnose syphilis by doing a blood test, or by looking at the blood under a microscope. Blood tests are used more often, because they are easier to do. However, blood tests cannot tell which stage of syphilis a person has.

Not having sexual contact with a person who has syphilis is one of the best ways to prevent getting syphilis.

If a person does not know if their sexual partner has syphilis, having safer sex can help protect them. For example, using a latexcondom the right way lowers the risk of getting a sexually transmitted disease like syphilis. However, even if a person uses a condom, it is still possible for him to get syphilis.[10][11]

Congenital syphilis in newborn babies can be prevented by testing mothers for syphilis during early pregnancy and treating women who are infected.[12] By following these steps, in 2015, Cuba became the first country in the world to eradicate the spread of syphilis from Cuban mothers to their babies.

In most developed countries, congenital syphilis is not common. It still happens once in a while, when women do not get any health care during pregnancy.[12] However, congenital syphilis is much more common in developing countries. Many women in these countries do not get healthcare during pregnancy, and others get healthcare that does not include testing for syphilis.[12] When there are programs that make syphilis testing easier to get, fewer babies get congenital syphilis in these countries.[14]

If people do certain things, they are more likely to get syphilis. Medical professionals say that these people should get tested regularly. For example, the CDC says that men who have sex with men should be tested at least every year.[15] Getting tested regularly helps prevent syphilis from being spread. If a person is tested and finds out that they have syphilis, they are more likely to get treatment, and will not accidentally spread syphilis to other people.

Syphilis is a notifiable disease in many places, including Canada,[16] the countries in the European Union,[17] and the United States.[18] This means that if a healthcare provider (like a doctor or a nurse) knows that a patient has syphilis, the provider has to tell public health authorities that the patient is infected. Public health workers then talk to all of the patient's sexual partners. They tell them someone might have given them syphilis, without telling them who that person is.[19] Doctors might also try to get patients with syphilis to tell their sexual partners to get treatment.[20]

Usually, people need just one dose of penicillin G or azithromycin.[21] If a person cannot take either of these medicines (for example, because they are allergic to them), some other medications work too. For example, Doxycycline and tetracycline are two other possible choices; however, they cannot be used in pregnant women.

Once a person is in the later stages of syphilis, the disease is harder to treat.

For example, if a person has neurosyphilis, they need antibiotics that will kill the infection in their central nervous system (their brain and major nerves). However, it is hard for penicillin G to get into the central nervous system. Because of this, a single shot of penicillin - which will usually cure early syphilis - is not enough to cure neurosyphilis. Instead, people with neurosyphilis usually need to be given large doses of penicillin for at least 10 days. Usually, they also need to get the medicine intravenously (through a needle placed into a vein) so it goes more directly to the central nervous system.[1][2] If a person is allergic to penicillin, other antibiotics like ceftriaxone, doxycycline, or tetracycline can be used, but they have to be given over longer periods of time.[2]

Once a person has late-stage syphilis, treatment will keep their syphilis from getting any worse. However, if syphilis has already damaged the person's body, the treatment will not make that damage go away. At best, treatment can only have a very small effect on the damage that has already happened.[2]

Syphilis used to be very common, and it caused sickness and death all over the world. It was especially very common in Europe during the 18th and 19th centuries. During the early 20th century, syphilis quickly became less common in the developed world, because antibiotics were being used more and more. Syphilis kept becoming less common until the 1980s and 1990s.[9] Since the year 2000, syphilis is getting more common again in the United States, the United Kingdom, Australia, and Europe, mostly among men who have sex with men.[1]

In China and Russia, syphilis has gotten more common among heterosexual ("straight") people since the 1990s.[1] Studies say this is because of unsafe sexual practices, like having sex with many different people, prostitution (getting paid to have sex), and not having safer sex to protect against sexually transmitted diseases.[1][24][25]

Over the 19th and 20th centuries, the symptoms of syphilis have become less severe (not quite as bad). This is partly because there are more treatments that work well, and if they are given early, syphilis does not get as bad. Also, the bacteria that causes syphilis has become weaker.[5]

If people with syphilis get treated early on, they can usually be cured without the disease causing damage that cannot be fixed.[4] However, syphilis is still very dangerous. It still causes serious problems, and sometimes death, if it is not treated.

Syphilis also makes a person two to five times more likely to get HIV. Confection (having both syphilis and HIV) is common. In some big cities, it happens in as many as 30% to 60% of people with syphilis.[1][2]

The earliest known medical drawing of people with syphilis, from Vienna (1498)

Nobody knows exactly where and how syphilis started.[2] There are two major ideas about where the disease came from.

The first idea is called the "Columbian hypothesis." (A hypothesis is an educated guess about how something happened). This hypothesis says that when Christopher Columbus's crew came back to Europe after exploring the "New World", they brought syphilis back to Europe and spread the disease there.

The other idea is called the "pre-Columbian hypothesis." ("Pre-Columbian" means "before Columbus.") This hypothesis says that syphilis was already in Europe before Columbus, and people just did not realize that the disease existed.[26]

While there is evidence that can be used to say that either of these ideas are right, there is more evidence for the Columbian hypothesis.[27]

The first written records that talk about an outbreak of syphilis in Europe are from 1494-1495. The outbreak happened in Naples, Italy, when France was invading (trying to take over Italy).[9][26] Because syphilis was spread by French soldiers who were coming back from Italy, at first it was called the "French disease."

The name "syphilis" was first used in 1530 by an Italian doctor and poet named Girolamo Fracastoreo. He used the word "syphilis" as the title of a Latin poem that talked about the damage the disease was causing in Italy.[28] At other times in history, syphilis was also called the "Great Pox".[29][30]

In 1905, two men named Fritz Schaudinn and Erich Hoffmann discovered that syphilis is caused by the Treponema pallidum bacteria.[9] Five years later, Paul Ehrlich created the first treatment that helped treat syphilis (called Salvarsan). After that, scientists started to study penicillin. In 1943, it was officially decided that penicillin worked for syphilis.[9][29]

This was a major success in the treatment of syphilis. Before penicillin, the treatments used for syphilis were often even worse than the disease. For example, people were treated with mercury (which is poisonous and causes serious health problems), or people were just kept away from everyone else.[29]

From 1932-1972, the United States Public Health Service did a study on syphilis in Alabama. They wanted to see how syphilis got worse when it was not treated. The researchers chose a group of poorAfrican-Americansharecroppers, but never told them they had syphilis. Even after the 1940s, when the researchers knew penicillin could cure these people, they refused to let them get treatment or even tell them that penicillin could help them. This study, now called the Tuskegee syphilis experiment, was very important in creating medical ethics.